Analysis of a lower jurassic geomagnetic reversal based on a model that relates transitional fields to variations of flux on the core surface

Abstract

For the last 12 Myr the transitional virtual geomagnetic poles (VGPs) of different reversals lie close to two preferred and practically antipodal longitudinal paths. In spite of some controversies about these transitional paths, it has been pointed out that they are linked to geomagnetic phenomena. Jurassic transitional VGP paths are quite similar to those of the last 12 Myr. Paleomagnetic data recorded in Stormberg Lavas (195 ± 5 Ma) belonging to two sampling localities of South Africa have been rotated according to an absolute palaeoreconstruction of Africa for the lower Jurassic. In order to avoid the hypothesis about dipolarity implicit in the VGPs calculations, the transitional directions recorded in the lavas were compared with others that were simulated on the basis of a model that relates transitional fields to variations of flux on the Earth's core surface. They were quite similar. For both, recorded and simulated data, the VGPs showed similar paths. Similar conditions could thus have driven both late Cenozoic and Jurassic reversals.